This invention relates to a connection structure and method for connecting an electric wire with a terminal by using ultrasonic vibration.
Japanese Unexamined Patent Application No.Hei7-70345 has disclosed an art for making a terminal into conductive contact with the cores of a covered wire by ultrasonic vibration, without peeling an insulating cover of the covered wire.
FIG. 5 shows a connector produced in this prior art method, which comprises a first member 1 and second member 2 which are formed of resin and assembled so as to oppose each other.
A groove portion 3 is formed on a top face of a first member 1 in the length direction thereof, and small concave portions 4 are formed at appropriate intervals in the length direction of the groove portion 3. Into the groove portion 3 of the first member 1 is inserted the terminal 5 along the length thereof and then a covered wire is placed on the terminal 5. The covered wire 6 is placed in a state in which a plurality of cores are covered with an insulating cover.
On a bottom of the second member 2 is formed a protrusion portion 7 which engages the groove portion 3 of the first member 1. Further, small convex portions 8 which engage the concave portions of the groove portion 3 are formed.
Upon assembly of the connector, with the terminal 5 and covered wire 6 inserted into the groove portion 3, the protrusion 7 of the second member 2 is engaged with the groove portion 3 of the first member 1, and the terminal 5 and covered wire 6 are pressed by means of the second member 2 and first member 1. At this time, where the convex portion 8 engages the concave portion 4, the terminal 5 and covered wire 6 are partially bent so as to act as a stopper against being loose.
Then, the first member 1 and second member 2 are pinched, and ultrasonic vibration is carried out by means of a horn (not shown). Due to heat generated by vertical vibration by the ultrasonic vibration, the insulating cover of the covered wire 6 is fused and removed out, so that the cores of the covered wire 6 and terminal 5 are made into contact with each other so that they are conductively contacted with each other. At the same time as this conductive contacting, the first member 1 and second member 2 are fused with each other, so that a connector containing the terminal 5 and wire is produced.
FIG. 6 shows a prior art structure for producing a multipolar connector. In a first member 1 are formed a plurality of the groove portions 3 and a second member 2 contains a plurality of protrusions 7 opposing the groove portions 3.
Upon assembly of the connector, the terminal is contained in each of the groove portions 3, and a covered wire is placed on the terminal. After that, these components are pressed by the first member 1 and second member 2, and then ultrasonic vibration is carried out in the same manner as described above.
In the structure shown in FIG. 6, small concave portions are formed in each of the groove portions 3 of the first member 1 like in the structure shown in FIG. 5 and small convex portions are formed on each of the protrusions 7 of the second member 2.
FIG. 7 shows a state in which the terminal 5 and covered wire 6 are pinched by the first member 1 and second member 2 having the above described structure. The terminal 5 and covered wire 6 are overlapped with each other by the pressing of the protrusion of the second member 2. A portion corresponding to the convex portion 8 and concave portion 4 is bent. Reference numerals 5a, 6a indicate these bent portions. Because the bent portions 5a, 6a are formed in the terminal 5 and covered wire 6 as described above, the connector is prevented from slipping out.
However, even if the terminal 5 and covered wire 6 are bent by the concave portions 4 and convex portions 8 so as to prevent them from slipping out, when a pulling tension is applied to the terminal 5 and covered wire 6, they are separated from each other, so that a contact area between the covered wire and terminal may be decreased. If the contact area between the cores and terminal is decreased, contact resistance of the entire connection portion between the terminal and cores is increased, so that generation of heat, deterioration of the material quality due to that generation of heat or other problem may occur.
Further, because the terminal 5 is bent by the concave portion 4 and convex portion 8, a dimension thereof must be determined taking this bent portion into account. Therefore, the dimension control of the terminal is troublesome.